Projection optical system, exposure apparatus incorporating this projection optical system, and manufacturing method for micro devices using the exposure apparatus

ABSTRACT

In a projection optical system which forms an image of a first plane on a second plane, using extreme ultraviolet illumination light, an object of the invention is to form an image on the first plane on the second plane under suitable conditions. This projection optical system comprises a first diffractive optical element arranged in an optical path between the first plane and the second plane; a second diffractive optical element arranged in the optical path on the side of the second plane from the first diffractive optical element; and an optical system having a negative power, arranged in the optical path between the first diffractive optical element and the second diffractive optical element.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a projection optical system forforming an image of a first plane on a second plane, an exposureapparatus incorporating this projection optical system and used at thetime of transferring a mask pattern onto a substrate in a lithographyprocess for manufacturing devices or micro devices, such assemiconductor devices or liquid-crystal display devices, and amanufacturing method for micro devices using this exposure apparatus tomanufacture micro devices such as semiconductor devices, imagingdevices, liquid-crystal display devices or thin film magnetic heads.

[0003] 2. Description of the Related Art

[0004] When micro devices such as semiconductor devices aremanufactured, there are used a batch exposure type projection exposureapparatus (stepper or the like) in which a minute pattern image formedon a reticle as a mask is transferred onto a wafer (or a glass plate) onwhich a resist is applied, via a projection optical system, or ascanning exposure type projection exposure apparatus involving a stepand scan method. In order to form a minute pattern on a wafer or thelike, it is necessary to increase the resolution of a pattern image ofthe reticle obtained by irradiating an illumination light onto thereticle.

[0005] As a method of increasing the resolution of the pattern image,there is a method involving making the illumination light mainly emittedfrom a light source a short wavelength, and a method involving designingthe numerical aperture (NA) of the projection optical system to be high.However, even if the numerical aperture of the projection optical systemis increased over and above what is required, if illumination lighthaving a long wavelength is used, there is naturally a limit toimprovement of the resolution. Therefore, it is basically necessary tomake the wavelength of the illumination light short. Heretofore, as thewavelength of illumination light, a g ray (436 nm) or an i ray (365 nm)has been often used. At present, however, the wavelength of illuminationlight has been made shorter, and a laser beam (248 nm) emitted from aKrF excimer laser or a laser beam (193 nm) emitted from an ArF excimerlaser is now being used. Moreover, a projection optical system which canbe used under exposure light having such a short wavelength is underdevelopment.

[0006] In evaluating the performance of the projection optical system,it is important to have a high numerical aperture, since this becomes anindex for obtaining a high resolution. However, even if the numericalaperture is high, if aberration occurs, there is a problem in formingminute patterns. Here, description is made of chromatic aberration, asone example of aberration. Since the optical performance of a projectionoptical system used in applications for forming minute patterns is quitehigh, it becomes necessary to make each aberration substantially zero.In order to make chromatic aberration zero, the projection opticalsystem has been heretofore realized by a dioptric system constituted byonly lens groups. This method however, requires a multiplicity oflenses, and hence invites a reduction in transmittance, and an increasein the cost for manufacturing the projection optical system cannot beavoided. Moreover, as is generally known, the condition for makingcurvature aberration of an image surface zero is to satisfy thePetzval's condition. In order to satisfy this condition however, it isnecessary to combine not only lenses having a positive power but alsolenses having a negative power. As a result, this is not desirable inview of improving transmittance and cost reduction.

[0007] As compared with dioptric optical elements such as lenses, in thediffractive optical elements, the reaction of chromatic aberration is ina direction opposite to that for the normal dioptric optical element.Therefore, by merely mixing the dioptric optical elements and thediffractive optical elements, chromatic aberration can be corrected.Moreover, since the diffractive optical element since power can be setto a predetermined value without making any contribution to thePetzval's condition, it is possible to make the image surface flat,designating curvature aberration as zero, without causing an increase inthe number of the dioptric optical elements. Also, since the diffractiveoptical element can optionally set the angle of diffraction, this has anadvantage in that it can be prepared as an optical element having asimilar action to that of an aspherical lens.

[0008] As described above, by using the diffractive optical element,chromatic aberration can be corrected and curvature aberration can bemade zero, without causing an increase in the number of the dioptricoptical lenses. This result is especially suitable for improvingtransmittance of the projection optical system and reducing the cost. Atechnique adopting such an optical system combining the diffractiveoptical element and the dioptric lens for the projection optical systemfor semiconductor manufacturing apparatus has been disclosed in, forexample, Japanese Unexamined Patent Application, First Publication Nos.Hei 1-307443, Hei 4-214516, Hei 6-331941, Hei 7-128590 and Hei 8-17719.

[0009] Below is a description of optical characteristic of thediffractive optical element. At the time of using the diffractiveoptical element, it is preferred to use a phase-type diffractive opticalelement (kinoform), in view of diffraction efficiency, and in view ofease of production the cross-section of the diffractive optical elementshould preferably be in a saw-tooth pattern (blazed type) or a stepwisepattern (binary optical element). Diffraction efficiency in this casestands for an intensity ratio between light incident on the diffractiveoptical element and diffracted light after predetermined order. With thediffractive optical element having a cross-section in a saw-toothpattern or a stepwise pattern, occurrence of unnecessary diffractedlight which does not contribute to image forming cannot be avoided dueto form error or the like. However, as disclosed in, for example,Japanese Unexamined Patent Application, First Publication No. Hei11-307443, when this unnecessary diffracted light has an intensity ratioand an intensity distribution of a desired numerical value or below, theinfluence thereof on the imaging performance can be substantiallyignored.

[0010] When the wavelength of illumination light becomes short withshortening of the wavelength of the light source, the kinds of usableglass material are limited due to absorption of light, and if thewavelength becomes 180 nm or below, the only glass material practicallyusable is fluorite. Therefore, under illumination light having such ashort wavelength, correction of chromatic aberration becomes impossiblewith a construction having only dioptric lenses. Hence it is necessaryto perform correction of chromatic aberration, using a diffractiveoptical element.

[0011] Moreover, when the exposure wavelength becomes ultraviolet light,it is necessary to form the ring width (pitch) around the diffractiveoptical element to be very small in order to obtain effective power forcorrecting the chromatic aberration, using the diffractive opticalelement. Hence the production thereof becomes difficult. In such a case,a diffractive optical element which obtains the power of the diffractiveoptical element within a range capable of production and reduces anoccurrence of unnecessary diffracted light as much as possible, and aprojection optical system using this diffractive optical element aredisclosed in Japanese Unexamined Patent Application, First PublicationNos. Hei 5-150107, Hei 5-297209 and Hei 6-331941.

[0012] However, for a projection optical system for forming a patternhaving a resolution of 0.1 μm or less, using extreme ultravioletillumination light having a large numerical aperture, measures have notheretofore been taken for exhibiting sufficient imaging performance,taking into consideration incident angle characteristics andmanufacturing error of the diffractive optical element.

[0013] In view of the above situation, a first object of the presentinvention is to provide a projection optical system that can form animage of a first plane on a second plane under suitable conditions,using extreme ultraviolet illumination light. Also, a second object ofthe present invention is to provide a projection optical system that canachieve the first object without causing a cost increase. Moreover, athird object of the present invention is to provide an exposureapparatus comprising such a projection optical system, which can form aminute pattern of 0.1 μm or less on a wafer arranged on the secondplane, and to provide a manufacturing method for micro devices, usingthis exposure apparatus.

SUMMARY OF THE INVENTION

[0014] In order to solve the above problems, a first aspect of thepresent invention is a projection optical system (PL) for forming animage on a first plane (P1) on a second plane (P2), comprising: a firstdiffractive optical element (Dl) arranged in an optical path between thefirst plane (P1) and the second plane (P2); a second diffractive opticalelement (D2) arranged in the optical path on the side of the secondplane (P2) from the first diffractive optical element (D1); and anoptical system (G2) having a negative power, arranged in the opticalpath between the first diffractive optical element (D1) and the seconddiffractive optical element (D2).

[0015] According to this projection optical system, an optical systemhaving a negative power is arranged in the optical path between thefirst diffractive optical element and the second diffractive opticalelement, so as to adjust the angle of incidence of the luminous fluxwhich is incident to the second diffractive optical element. Therefore,the luminous flux can be diffracted according to the diffractioncharacteristic of the second diffractive optical element, and as aresult, the image on the first plane can be formed on the second planewith high precision. Hence, the system is especially suitable forforming an image of a minute pattern, in particular, a pattern of 0.1 μmor less on the second plane.

[0016] Moreover, this projection optical system (PL) further comprises:a front optical system (G1) arranged in an optical path between thefirst plane (P1) and the first diffractive optical element (D1); and arear optical system (G3) arranged in an optical path between the seconddiffractive optical element (D2) and the second plane (P2); and thefront optical system (G1) converts an axial luminous flux on the firstplane (P1) to substantially parallel luminous flux, and guides theparallel luminous flux to the first diffractive optical element (D1);and the optical system (G2) having a negative power converts an axialluminous flux on the first plane (P1) via the first diffractive opticalelement (D1) again to substantially parallel luminous flux, and guidesthe parallel luminous flux to the second diffractive optical element(D2).

[0017] According to this projection optical system, the axial luminousflux on the first plane is converted to a substantially parallelluminous flux, and shone onto the first diffractive optical element, andthe axial luminous flux on the first plane via the first diffractiveoptical element is again converted to a substantially parallel luminousflux and guided to the second diffractive optical element. As a result,the image on the first plane can be formed on the second plane with highprecision. Moreover, the first diffractive optical element and thesecond diffractive optical element have a chromatic aberrationcharacteristic opposite to that of a chromatic aberration caused by thefront optical system, the rear optical system and the optical systemhaving a negative power, and do not affect the Petzval's condition.Hence the chromatic aberration can be corrected favorably. As a result,the system is especially suitable for forming an image on the firstplane on the second plane with high precision. Furthermore, sincecorrection of chromatic aberration is performed only by the diffractiveoptical element, several lenses arranged in the optical path forcorrecting the chromatic aberration are not required, thereby keepingdown cost increase. Also, even if chromatic aberration cannot becorrected by lenses, due to a restriction on the glass material of thelenses, chromatic aberration can be corrected by using a diffractiveoptical element having an aberration characteristic opposite to that oflenses. Furthermore, since two diffractive optical elements, namely thefirst diffractive optical element and the second diffractive opticalelement, are used to obtain a power required for correction of chromaticaberration by each diffractive optical element, even if values ofchromatic aberration in the front optical system, the rear opticalsystem and the optical system having a negative power are varied,chromatic aberration can be properly corrected.

[0018] Furthermore, a second aspect of the present invention is aprojection optical system (PL) for forming an image on a first plane(P1) on a second plane (P2), comprising: diffractive optical elements(D1, D2) arranged in an optical path between the first plane (P1) andthe second plane (P2); and optical systems (G1, G2) arranged in anoptical path between the first plane (P1) and the diffractive opticalelements (D1, D2), wherein when a numerical aperture on the side of thesecond plane (P2) of the projection optical system (PL) is designated asNA, an imaging magnification of the optical systems (G1, G2) from thefirst plane (P1) to immediately before the diffractive optical elements(D1, D2) is designated as β, the focal length of the diffractive opticalelements (D1, D2) with respect to a predetermined wavelength isdesignated as f, and the distance from the first plane (P1) to thesecond plane (P2) is designated as L, the projection optical systemsatisfies the following conditions:

1/|NA·β|<0.7

0.38<f/L<1.2.

[0019] According to this projection optical system, by satisfying theabove described conditions, a projection optical system having a largenumerical aperture, but having no imaging performance degradation due tothe angular characteristic can be realized. Hence sufficient correctionof chromatic aberration can be realized. Moreover, by satisfying theabove described conditions, the pitch of the diffractive opticalelements is not refined so much, and diffractive optical elements havinga relatively wide pitch and which are easy to manufacture can be used.

[0020] Furthermore, a third aspect of the present invention is aprojection optical system (PL) having a plurality of optical elementsarranged along an optical path between a first plane (P1) and a secondplane (P2) for forming an image on the first plane (P1) on the secondplane (P2), wherein at least one diffractive optical element (D1, D2)having a diffraction pattern surface (PL1, PL11) formed on one surfaceand a correction surface (PL2, PL22) formed on an other surface isarranged along the optical path, and the correction surface (PL2, PL12)corrects a manufacturing error on the diffraction pattern surface (PL1,PL11).

[0021] According to this projection optical system, since a correctionsurface for correcting a manufacturing error on the diffraction patternsurface is formed on the diffractive optical element, the system isespecially suitable as a diffraction grating used for a projectionoptical system where extremely high precision imaging characteristicsare required.

[0022] Moreover, this projection optical system (PL) is characterized inthat the correction surface (PL2, PL12) has a slightly aspheric surfacewhich has been subjected to aspheric surface processing with a sagamount of 0.5 μm or less with respect to a predetermined referenceplane, and that the reference plane is a flat or spherical surface.

[0023] The present invention is also characterized in that in theprojection optical system (PL) according to the first to third aspectsof the invention, all the diffraction patterns of the diffractiveoptical elements (D1, D2) are formed on a flat substrate.

[0024] Moreover, the present invention is characterized in that in theprojection optical system (PL) according to the first to third aspectsof the invention, diffraction patterns of the diffractive opticalelements (D1, D2) are formed in a plurality of ring areas centered on anoptical axis (AX), each ring area being formed of a binary opticalelement approximated in a plurality of stages by a plurality ofsurfaces, and the binary optical element formed in each ring area has apositive power, respectively. Here, it is desired that of respectivebinary optical elements respectively formed in each ring area, at leastone stage is made different from others, or that a filter having adifferent transmittance according to each ring area is arranged in thevicinity of the diffractive optical element.

[0025] The present invention is also characterized in that in theprojection optical system (PL) according to the first to third aspectsof the invention, the diffraction patterns of the diffractive opticalelements (D1, D2) are formed in a plurality of ring areas centered on anoptical axis (AX), and each of the respective ring areas has a sawtoothcross-section having a positive power. Here, it is desired that thediffraction pattern of the diffractive optical element is formed in afirst ring area and a second ring area, centered on a mutual opticalaxis, the first ring area being formed on the side of the optical axisfrom the second ring area, and having a sawtooth cross-section in whichthe diffraction efficiency becomes highest with regard to the 1st or−1st diffracted light, and the second ring area being formed on the sideof the peripheral from the first ring area, and having a sawtoothcross-section in which the diffraction efficiency becomes highest withregard to the mth or - mth diffracted light (m is an integer equal to orgreater than 2).

[0026] Also, it is desired that the plurality of optical elementsconstituting the projection optical system (PL) of the above describedfirst to third aspects of the invention have lenses contributing toforming an image on the first plane (P1) on the second plane (P2), andthat all the lenses constituting the projection optical system beconstituted of fluorite. Moreover, it is desired that the optical system(G2) having a negative power has an aspheric surface.

[0027] Furthermore, the projection optical system (PL) of a fourthaspect of the invention is characterized in that a plurality of opticalelements are respectively arranged along an optical path between a firstplane and a second plane for forming an image on the first plane (P1) onthe second plane (P2), and at least one of these plurality of opticalelements has an optical surface (PL1) formed on one surface and acorrection surface (PL2) formed on an other surface, and the correctionsurface (PL2) corrects a manufacturing error on the optical surface(PL1).

[0028] According to this projection optical system, since amanufacturing error on the optical surface formed on the optical elementis corrected by means of the correction surface, the system isespecially suitable as an optical element used for a projection opticalsystem wherein an image quality having extremely high precision isrequired.

[0029] In the projection optical system (PL) of the above fourth aspectof the invention, it is desired that the correction surface (PL2) has aslightly aspheric surface which has been subjected to aspheric surfaceprocessing with a sag amount of 0.5 μm or less with respect to apredetermined reference plane.

[0030] Furthermore, the projection optical system (PL) of the secondaspect of the invention according to the present invention ischaracterized in that an optical system (G3) having a positive power isarranged in the optical path between the diffractive optical element(D1, D2) and the second plane (P2), and the optical system (G1) arrangedin the optical path between the first plane (P1) and the diffractiveoptical element (D1, D2) has a positive power.

[0031] An exposure apparatus of the present invention is characterizedby comprising: a mask stage (14) for setting a mask (R) having apredetermined pattern formed thereon on the first plane (P1); asubstrate stage (22) for setting a photosensitive substrate (W) on thesecond plane (P2); an illumination optical system (10, IL) forilluminating the mask (R) set on the first plane (P1); and a projectionoptical system according to either one of the above first to fourthaspects of the invention, for performing projection exposure of apattern image of the mask (R) on the photosensitive substrate (W).

[0032] According to this exposure apparatus, the pattern image formed onthe mask arranged on the first plane can be formed with high precisionon the photosensitive substrate arranged on the second plane. As aresult, the apparatus is extremely suitable for forming a minutepattern, especially, a minute pattern of 0.1 μm or less on the wafer.

[0033] A manufacturing method for micro devices according to the presentinvention is characterized by including: a first setting step forsetting a mask (R) having a predetermined pattern on the first plane(P1); a second setting step for setting a photosensitive substrate (W)on the second plane (P2); an illumination step for illuminating the mask(R); an exposure step for performing projection exposure of the patternimage of the mask (R) on the photosensitive substrate (W), using aprojection optical system according to either one of the above first tofourth aspects of the invention; and a development step for developingthe photosensitive substrate (W) to which the image has beentransferred.

[0034] According to this manufacturing method for micro devices, as inthe above described exposure apparatus, the pattern image formed on themask arranged on the first plane can be formed with high precision onthe photosensitive substrate arranged on the second plane. As a result,the method is extremely suitable for manufacturing micro devices whereit is necessary to form a minute pattern, especially, a minute patternof 0.1 μm or less on the wafer.

BRIEF DESCRIPTION OF DRAWINGS

[0035]FIG. 1 is a diagram showing a schematic construction of anexposure apparatus according to one embodiment of the present invention,comprising a projection optical system according to one embodiment ofthe present invention.

[0036]FIG. 2 is a cross-sectional view of a lens, showing a basicoptical construction of the projection optical system according to oneembodiment of the present invention.

[0037]FIG. 3A is a perspective view schematically showing one embodimentof the construction of a diffractive optical element.

[0038]FIG. 3B is a cross-sectional view schematically showing oneembodiment of the construction of a diffractive optical element.

[0039]FIG. 4 is a diagram for explaining one example of a method offorming a binary optical element.

[0040]FIG. 5A is a perspective view schematically showing an otherembodiment of the construction of the diffractive optical element.

[0041]FIG. 5B is a cross-sectional view schematically showing an otherembodiment of the construction of the diffractive optical element.

[0042]FIG. 6 is a diagram showing a situation where illumination lightvia a projection optical system is irradiated onto a wafer.

[0043]FIG. 7 is a cross-sectional view of a lens showing the opticalconstruction of the projection optical system according to oneembodiment of the present invention.

[0044]FIG. 8 is a diagram showing a transverse aberration diagram(comatic aberration diagram) in the tangential direction and the sagitaldirection of the projection optical system according to one embodimentof the present invention.

[0045]FIG. 9 is a cross-sectional view of a lens showing the opticalconstruction of a projection optical system according to an otherembodiment of the present invention.

[0046]FIG. 10 is a diagram showing a transverse aberration diagram(comatic aberration diagram) in the tangential direction and the sagitaldirection of the projection optical system according to the otherembodiment of the present invention.

[0047]FIG. 11 is a flowchart showing a manufacturing example for microdevices.

[0048]FIG. 12 is a diagram showing one example of a detailed flow instep S13 in FIG. 11, at the time of manufacturing semiconductor devices.

PREFERRED EMBODIMENTS

[0049] A projection optical system according to the embodiments of thepresent invention, an exposure apparatus comprising this projectionoptical system and a manufacturing method for micro devices using thisexposure apparatus will now be described in detail, with reference todrawings.

[0050]FIG. 1 is a diagram showing a schematic construction of anexposure apparatus according to one embodiment of the present invention,comprising a projection optical system according to one embodiment ofthe present invention. In this embodiment, description is made for acase where a cata-dioptric system is used as the projection opticalsystem. In the description below, an XYZ rectangular coordinate systemshown in FIG. 1 is set, and positional relation between respectivemembers is described, with reference to this XYZ rectangular coordinatesystem. The XYZ rectangular coordinate system is set such that theY-axis and the Z-axis are parallel to the page, and the X-axis isperpendicular to the page. Also in the cata-dioptric system constitutingthe projection optical system PL as the projection optical systemaccording to one embodiment of the present invention, the referenceoptical axis AX is set to be parallel to the Z-axis. However, in the XYZcoordinate system in the figure, the X-Y plane is actually set on aplane parallel to the horizontal plane, and the Z-axis is set in theperpendicular direction. In this specification, the term “power” is notlimited to refracting power of the diffractive optical element, and isused as a word meaning an inverse number of the focal length. Therefore,the term “power” also means an inverse number of the focal length of,for example, a reflecting type diffractive optical element.

[0051] The exposure apparatus shown in FIG. 1 comprises a light source10 for supplying illumination light in the ultraviolet region. For thislight source 10, for example, a KrF excimer laser (emission wavelength:248 nm), an ArF excimer laser (emission wavelength: 193 nm) or an F2excimer laser (emission wavelength: 157.624 nm) is used. The lightemitted from the light source 10 uniformly illuminates a reticle Rhaving a predetermined pattern formed thereon, via an illuminationoptical system IL. The optical path between the light source 10 and theillumination optical system IL is sealed with a casing (not shown), andthe space from the light source 10 up to the optical member closest tothe reticle R side in the illumination optical system IL is replacedwith an inert gas such as helium or nitrogen, being a gas having a lowrate of absorption of the exposure light, or is substantially held in avacuum condition.

[0052] The reticle R serving as a mask, is held on a reticle stage 14serving as a mask stage, via a reticle holder 12, in parallel to the X-Yplane, and is set on the first plane referred to in the presentinvention. A predetermined pattern to be transferred is formed on thereticle R, and of the whole pattern area, a rectangular (slit-shaped)pattern area having a long side along the X-axis direction and a narrowside along the Y-axis direction is illuminated. The reticle stage 14 istwo-dimensionally movable along the plane of the reticle (that is, theX-Y plane) by operation of a drive system (not shown), and the positioncoordinate thereof is measured by an interferometer 18 using a reticlemovable mirror 16, and the position is controlled.

[0053] The pattern image formed on the reticle R forms a reticle patternimage on a wafer W serving as a photosensitive substrate, via acata-dioptric projection optical system PL. The wafer W is held inparallel to the X-Y plane on a wafer stage 22 serving as a substratestage, via a wafer holder 20, and the surface thereof is set on thesecond plane referred to in the present invention. Then, the patternimage is formed in a rectangular exposure area having a long side alongthe X-axis direction and a narrow side along the Y-axis direction on thewafer W, so as to optically correspond to the rectangular illuminationarea. The wafer stage 22 is two-dimensionally movable along the plane ofthe wafer (that is, the X-Y plane) by operation of a drive system (notshown), and the position coordinate thereof is measured by aninterferometer 26 using a wafer movable mirror 24, and the position iscontrolled.

[0054] The construction is also such that the inside of the projectionoptical system PL is kept in an airtight condition, between the opticalmember arranged closest to the reticle side and the optical memberarranged closest to the wafer W side, of the optical membersconstituting the projection optical system PL provided in the exposureapparatus shown in FIG. 1, and the inside of the projection opticalsystem PL is replaced with an inert gas such as helium or nitrogen, oris substantially held in the vacuum condition. Moreover, in the narrowoptical path between the illumination optical system IL and theprojection optical system PL, the reticle R, the reticle stage 14 andthe like are arranged. The inside of a casing (not shown) for sealingand enclosing the reticle R, the reticle stage 14 and the like is filledwith an inert gas such as nitrogen or helium gas, or is substantiallyheld in the vacuum condition. Also, on the projecting surface side ofthe projection optical system PL, there are arranged the wafer W, thewafer stage 22, and the like, and the inside of a casing (not shown) forsealing and enclosing the wafer W, the wafer stage 22 and the like isfilled with an inert gas such as nitrogen or helium gas, or issubstantially held in the vacuum condition. In this manner, anatmosphere in which the exposure light is hardly absorbed is formedthroughout the optical path from the light source 10 to the wafer W.

[0055] As described above, the illumination area on the reticle R andthe exposure area on the wafer W (that is, the effective exposure area)regulated by the projection optical system PL is in a rectangular shapehaving a narrow side along the Y-axis direction. Therefore, whileperforming position control of the reticle R and the wafer W, using thedrive system and the interferometers 18, 26, by synchronously moving(scanning) the reticle stage 14 and the wafer stage 22 and consequently,the reticle R and the wafer W in the same direction (that is, toward thesame direction), in the direction of the narrow side of the rectangularexposure area and the illumination area, that is, along the Y-axisdirection, a pattern formed on the reticle R is scanned and exposed onthe area on the wafer, having a width equal to the long side of theexposure area and having a length corresponding to the scanning amount(shift amount) of the wafer W.

[0056] In the above description, description has been made of anexposure apparatus of the so-called step and scan method, wherein thereticle R and the wafer W are synchronously moved with respect to theprojection optical system PL, and a pattern formed on the reticle R istransferred onto the wafer W. However, this may be exposure apparatus ofthe so-called step and repeat method (a so-called stepper). The step andrepeat method is a method wherein the operation is repeated such that awafer stage 22 is driven step by step, to thereby adjust the position ofeither one of a plurality of shot areas set on the wafer W with respectto the projection area of the projection optical system PL, and thepattern image formed on the reticle R is transferred onto the positionedshot area.

[0057] The exposure apparatus according to one embodiment of the presentinvention has been roughly described above. A projection optical systemaccording to the one embodiment of the present invention, provided inthe exposure apparatus according to one embodiment of the presentinvention will now be described in detail, with reference to drawings.

[0058]FIG. 2 is a cross-sectional view of a lens showing a basic opticalconstruction of a projection optical system according to one embodimentof the present invention. In FIG. 2, the basic construction of theprojection optical system PL is such that there are arranged, in orderfrom a reticle R set on the first plane (object surface) P1, an opticalsystem Gi, a diffractive optical element D1, an optical system G2, adiffractive optical element D2, and an optical system G3. The projectionoptical system PL is telecentric both on the reticle R (object surface)side, and on the wafer W (image surface) side arranged on the secondplane (image surface).

[0059] The optical system Gi comprises, in order from the first planeP1, a double-convex positive lens LI, a double-concave lens L2, and aplano-convex lens L3 with the convex surface facing the second plane P2,and is designed so as to have a positive power as a whole. This opticalsystem Gi converts an axial luminous flux on the first plane P1 tosubstantially a parallel luminous flux, and guides this parallelluminous flux to the diffractive optical element D1, and constitutes afront optical system referred to in the present invention. Here, thereason why the axial luminous flux on the first plane P1 is converted tosubstantially a parallel luminous flux is described hereunder. In thediffractive optical element D1, the diffraction efficiency changesdepending on the angle of incidence of the incident light. Hence if aluminous flux such as divergent luminous flux or convergent luminousflux is shone thereon, the image quality is degraded. Therefore, this isto prevent degradation of the image quality of the diffractive opticalelement D1, by reducing a variation in the angle of incidence of theincident luminous flux as much as possible.

[0060] As described above, when a wavelength of light emitted from thelight source 10 is about 200 μm, or when a wavelength shorter than 200μm is used, the glass material for the lenses L1 to L3 constituting theoptical system Gi or the lenses constituting the optical system G3 isrestricted. Particularly, when an F2 excimer laser (emission wavelength:157.624 nm) is used for the light source 10, all of the lenses L1 to L3constituting the optical system G1 are formed of fluorite.

[0061] The diffractive optical element D1 is provided for correctingchromatic aberration. Here, the reason for correcting chromaticaberration by using the diffractive optical element D1 is because thelight emitted from the light source 10 in FIG. 1 is light having a shortwavelength of about 200 μm, and hence the glass material of lenses thatcan be arranged on the optical path is restricted. That is to say, whenthe projection optical system PL is constituted of a single glassmaterial, insufficient correction of chromatic aberration by means of apositive lens occurs. Hence chromatic aberration due to the lenses iscorrected, by using a diffractive optical element having a chromaticaberration characteristic opposite to that of the normal lenses, as thediffractive optical element Dl. Here, the chromatic aberrationcharacteristic which a normal lens has is an aberration characteristicattributable to a characteristic where dispersion increases as thewavelength becomes short. The diffractive optical element D1 is designedso as to have a positive power in order to correct chromatic aberrationof a positive lens.

[0062] The optical system G2 is an optical system having a negativepower referred to in the present invention, and is provided forconverting the axial luminous flux on the first plane P1 diffracted bythe diffractive optical element D1 to substantially a parallel luminousflux and guiding the parallel luminous flux to the diffractive opticalelement D2. Here, the axial luminous flux on the first plane P1diffracted by the diffractive optical element D1 is converted again to asubstantially parallel luminous flux by the optical system G2, for thesame reason as in the above described optical system D1. That is to say,in the diffractive optical element D2, the diffraction efficiencychanges depending on the angle of incidence of the incident light. Henceif a luminous flux diffracted by the diffractive optical element D1 isdirectly shone thereon, the image quality of the diffractive opticalelement D2 is degraded. Therefore, degradation in the image quality ofthe diffractive optical element D2 is prevented, by reducing variationsin the incident luminous flux as much as possible, by converting theluminous flux incident on the diffractive optical element D2 into aparallel luminous flux.

[0063] Here, the reason why two diffractive optical elements, namely thediffractive optical element D1 and the diffractive optical element D2,are provided is as follows. That is to say, the diffractive opticalelement D1 and the diffractive optical element D2 are provided forcorrecting chromatic aberration due to the lenses arranged on theoptical path, as described above, and in order to correct this chromaticaberration, a power higher than a certain level is required. Therefore,if for example, an attempt is made to obtain a power which can correctchromatic aberration of lenses with only a single diffractive opticalelement Dl, by omitting the diffractive optical element D2 and theoptical system G2, the lattice spacing (pitch) of the diffractiveoptical element D1 becomes quite narrow, since the wavelength of lightemitted from the light source 10 is 200 μm or less. Actually, however,it is difficult to manufacture a diffractive optical element having apitch of 1 μm or less. Therefore, by arranging two diffractive opticalelements, that is, the diffractive optical element D1 and thediffractive optical element D2 shown in FIG. 2, on the optical path, thepower required for correction of chromatic aberration is obtained.

[0064] As described above, a projection optical system having sufficientchromatic aberration correcting ability, but without having degradationin the image quality due to the angular characteristic can be realized,by arranging a plurality of diffractive optical elements D1 anddiffractive optical elements D2 in the optical path and arranging theoptical system G1 in the optical path in the previous stage of thediffractive optical element D1, as well as arranging the optical systemG2 having a negative power between the diffractive optical element D1and the diffractive optical element D2, to thereby allow a parallelluminous flux to enter with respect to the diffractive optical elementD1 and the diffractive optical element D2. In FIG. 2, there is shown,for the optical system G2, a refractive optical system, for example, adouble-concave lens as an example. However, the optical system G2 needonly have a negative refractive index, and for example, it may be areflecting optical system such as a convex reflecting mirror or thelike.

[0065] The optical system G3 comprises, in order from the first planeP1, a double-convex positive lens L4, and a plano-convex lens L5 withthe convex surface facing the first plane P1, and is designed so as tohave a positive power as a whole. This optical system G3 is for imageformation on the second plane P2, that is, the wafer W, by the lightdiffracted by the diffractive optical element D2, and has a positivepower and constitutes a rear optical system referred to in the presentinvention. As described above, when a wavelength of light emitted fromthe light source 10 is about 200 μm, or when a wavelength shorter than200 μm is used, the glass material for the lens L4 and lens L5constituting the optical system G3 is restricted. Particularly, when anF2 excimer laser (emission wavelength: 157.624 nm) is used for the lightsource 10, all of the lens L4 and lens L5 constituting the opticalsystem G3 are formed of fluorite.

[0066] In order to make the resolution of the exposure apparatus 0.1 μmor less, it is essential to use light having a wavelength shorter than180 μm as the wavelength of light emitted from the light source 10.However, by using fluorite for the material of all lenses constitutingthe projection optical system PL, absorption of light due to the lensesdecreases, and the wafer W can be exposed by illumination light havinghigh light intensity, thereby enabling realization of a high throughput.For the substrate of the diffractive optical elements D1 and D2, anymaterial having an internal transmittance of 70% or higher may be used,by making the thickness sufficiently thin.

[0067] Here, when a numerical aperture on the second plane P2 side ofthe projection optical system PL shown in FIG. 2 is designated as NA,the imaging magnification of the optical system G1 is designated as β,the focal length of the diffractive optical element D1 and thediffractive optical element D2 with respect to the wavelength of lightemitted from the light source 10 is designated as f, and the distancefrom the first plane P1 to the second plane P2 is designated as L, it isdesirable to satisfy the following expression (1) and expression (2):

1/|NA·β|<0.7  (1)

0.38<f/L<1.2  (2)

[0068] The above expression (1) is an expression representing conditionsfor realizing a projection optical system PL having a large numericalaperture, but without having degradation in the image quality due to theangular characteristic. In the expression (1), it is more desirable thatthe value of 1/|NA·β| is smaller than 0.55. Moreover, the aboveexpression (2) is an expression representing conditions for realizingsufficient correction of chromatic aberration by means of thediffractive optical element D1 and the diffractive optical element D2.In the expression (2), if the value of f/L becomes equal to or below avalue of the lower limit 0.38, diffractive optical elements D1 and D2having a quite narrow pitch must be manufactured, thereby making itdifficult to manufacture the diffractive optical elements D1 and D2. Asdescribed above, the lower limit in the expression (2) is a valuedetermined by the ease of production of the diffractive optical elementsD1 and D2. Moreover, the upper limit in the expression (2) is anexpression representing conditions for obtaining a sufficient power forcorrecting chromatic aberration of the projection optical system PL, andif the value of f/L becomes equal to or higher than the value of theupper limit 1.2, sufficient correction of chromatic aberration cannot beperformed. Also in the expression (2), taking the ease of production ofthe diffractive optical elements and the degree of chromatic aberrationcorrection into consideration, it is further desired that the value off/L be smaller than 0.42 and larger than 1.0. Furthermore, whenhigher-order diffracted light is used as the imaging light, or when thenumerical aperture NA exceeds 0.7, it is desirable that all thediffractive optical elements arranged in the projection optical systemPL satisfy the above expressions (1) and (2).

[0069] Next, the structure of the diffractive optical elements D1 and D2will be described.

[0070] At first, one embodiment of the structure of the diffractiveoptical elements D1 and D2 will be described. FIGS. 3A and 3B arediagrams schematically showing one embodiment of the structure of thediffractive optical elements D1 and D2, with FIG. 3A being a perspectiveview and FIG. 3B being a cross-sectional view. As shown in FIGS. 3A and3B, at least one of the diffractive optical elements D1 and D2 has,other than a diffraction pattern surface PL1 having a diffractionpattern formed thereon, a correction surface PL2 for correcting anymanufacturing error on the diffraction pattern surface PL1. On thediffraction pattern surface PL1, there are formed a plurality of ringareas k1 to k5 having a positive power, in concentric circles centeredon the optical axis AX, with a binary optical element formed in eachring area k1 to k5. As shown in FIG. 3B, the binary optical elementformed in each ring area k1 to k5 is obtained by forming the surface ofa Fresnel ring-plate in a stepped form, and it is normally formed forincreasing the diffraction efficiency of the ring plate.

[0071] Here, a method of forming the binary optical element will bebriefly described. FIG. 4 is a diagram for explaining one example of amethod of forming the binary optical element. At first, as shown in step(a) in FIG. 4, a first etching stopper layer “A” is provided on a flatsubstrate “0”, a first transparent layer “1” comprising a SiO₂ film isformed by deposition, and further, a Cr film formed in, for example, 50nm is prepared on the first transparent layer “1” continuously by anelectron-beam evaporation technique. This becomes a substrate to beprocessed. Next, a photoresist is applied on the substrate having thefirst etching stopper layer “A” and the Cr film formed on the firsttransparent layer “1” by an application method such as spin coating, andthe photoresist is subjected to baking to form a resist layer having athickness of about 0.5 μm. Subsequently, such a substrate is carriedinto an exposure apparatus or the like for performing rotating exposure,and a pattern image on a reticle formed thereon, having a patterncorresponding to a two-stage structure, of for example an eight-stagelayered structure, is transferred onto the substrate depending on thebinary optical element to be designed.

[0072] When transfer of various patterns has been completed, thesubstrate having a first resist pattern formed thereon is placed in areactive ion etching apparatus, to etch the Cr according to the firstresist pattern, and to remove the resist provided on the substrate W,after the Cr etching. Due to the above operation, the resist pattern istransferred to the Cr film. Subsequently, this Cr pattern is masked, toetch the first transparent layer “1” being in contact with the airsurface. After etching, the Cr being a mask is removed, and through apure water rinse and drying step, a first transparent pattern “1 a” isformed, with the first etching stopper layer “A” exposed (see step (b)in FIG. 4). An Al₂O₃ film is then deposited only on the upper part ofthe first transparent pattern “1 a”, formed in this manner, to form asecond etching stopper layer “B” (step (c) in FIG. 4). In this case, forexample, by a method in which a resist is applied on the exposed firststopper layer “A”, and Al₂O₃ on the resist is the removed together withthe resist, the second etching stopper layer “B” is formed only on theupper part of the first transparent pattern “1 a”. As a result, apattern having a two-stage layered structure is formed.

[0073] Moreover, by a similar method to the one shown in step (a) inFIG. 4, a second transparent layer “2” is formed on the surfaces of theexposed first stopper layer “A” and the second stopper layer “B” (seestep (d) in FIG. 4). Then, continuously, a Cr film is formed on thesecond transparent layer “2”, and a resist is applied by spin coating onthis Cr film, and the resist is subjected to baking, to form a resistlayer having a thickness of about 0.5 μm. Subsequently, processing forexposing the resist on the second transparent layer “2” is performed,using a reticle having a pattern corresponding to the four-stagestructure, of the eight-stage layered structure, depending on thepattern to be formed. This second resist pattern is used as a mask toetch the Cr film on the second transparent layer “2” to transfer thepattern, and thereafter the second resist pattern is removed. Then, thisCr pattern is used as a mask to perform reactive ion etching of thesecond transparent layer “2” under the same conditions as those of theetching step of the first transparent layer “1”, to thereby form asecond transparent layer pattern 2a (see step (e) in FIG. 4).

[0074] Next, an Al₂O₃ film is deposited only on the upper part of thesecond transparent pattern 2a, to form a third etching stopper layer C(see step (f) in FIG. 4). At this point of time, a pattern of thefour-stage layered structure has been formed. Further, a pattern of aneight-stage layered structure is formed, by repeating the same stepsuntil the above four-stage layered structure is formed. That is to say,a third transparent layer 3 is formed over the exposed whole surface ofthe first stopper layer “A”, the second stopper layer “B” and the thirdstopper layer “C” (see step (g) in FIG. 4). After the Cr film and theresist layer have been formed on these third transparent layers 3, thepattern image is exposed on the resist layer, using the reticle patterncorresponding to the diffraction pattern of the eight-stage layeredstructure, and then transferred to the Cr film sequentially. Using theCr pattern formed in this manner as a mask, reactive ion etching isperformed on the third transparent layer 3, to thereby form a thirdtransparent layer pattern 3a (see step (h) in FIG. 4).

[0075] Through the above steps, a diffractive optical element having thebinary optical element shown in FIG. 3B formed thereon can be obtained.As described above, the diffraction pattern of the diffractive opticalelements D1 and D2 are formed on a flat substrate. If the diffractionpattern surfaces of the diffractive optical elements D1 and D2 areformed on the flat substrate, a lithography process using an exposureapparatus becomes possible, enabling production of a diffractive opticalelement comprising a finer pattern. Moreover, by making a binary opticalelement in which the ring areas k1 to k5 are formed in concentriccircles, centered on the optical axis AX, with each ring approximated ina stepped form by means of a plurality of surfaces, the manufacturingprocess can be simplified, and high-precision patterns can be produced.

[0076] The number of stages of the binary optical elements formed in thering areas of the diffractive optical elements D1 and D2 shown in FIG.3B are formed the same (for example, eight stages). However, since thering areas in the vicinity of the periphery of the diffractive opticalelements D1 and D2 have a narrow pitch, in many cases, it becomes moredifficult to manufacture these stages, compared to the production of thestages of the binary optical element formed in the paraxial area withrespect to the optical axis AX. In such a case, the number of stages ofthe binary optical element formed in the ring areas in the vicinity ofthe periphery of the diffractive optical elements D1 and D2 may bereduced. For example, by changing the number of stages of the stepswhich form each ring depending on the area, such that the vicinity ofthe periphery having a narrow pitch (for example, the ring areas k4, K5in FIG. 3A) has four stages, the central part largely affected by theunnecessary diffracted light (for example, the ring area k1 in FIG. 3A)has 16 stages, and the middle part (for example, the ring areas k2, k3in FIG. 3A) has 8 stages, a diffractive optical element which isminimally affected by the unnecessary diffracted light can be obtained,in a manufacturable pattern and with higher diffraction efficiency as awhole. Moreover, the number of stages of the binary optical element isnot always such that there are many stages formed in the ring areas inthe vicinity of the optical axis AX, and a few stages formed in the ringareas in the vicinity of the periphery of the diffractive opticalelements D1 and D2, and the number of stages of the binary opticalelement can be appropriately set according to the required diffractionperformance.

[0077] Furthermore, the number of stages in each ring area formed in thediffractive optical elements D1 and D2 is changed not only to facilitatethe production of the diffractive optical elements D1 and D2, but alsoto decrease flare light reaching the wafer W. Here, the flare lightstands for the unnecessary order of light diffracted by the diffractiveoptical elements D1 and D2. In order to form an image of a patternformed on the reticle R on the wafer W with high precision, it isdesired to reduce the flare light as much as possible. Here, of theflare light caused in the projection optical system PL, much of theflare light passing through the paraxial area of the optical axis AXreaches the wafer W, and the flare light passing through the far-axialarea has a low rate of proceeding to out of the lens and reaching thewafer W. Therefore, in the paraxial area, the pitch of the diffractiveoptical elements D1 and D2 is designed to be narrow so as to suppressthe occurrence of the unnecessary flare light and to increase thediffraction efficiency to the necessary order, and in the far-axialarea, the pitch is designed to be wide, since even if the rate ofoccurrence of the flare light is relatively high, the rate of flarelight reaching the wafer W is low.

[0078] As described above, when the number of stages of the binaryoptical element formed in each ring area is changed, since the intensitydistribution of the image-forming light is changed step-wise in theboundary where the number of stages is changed, degradation in the imagequality may occur. That is to say, for example, if the number of stagesdecreases in the vicinity of the periphery of the diffractive opticalelements D1 and D2, deviation from the Fresnel ring-plate increases, andhence the diffraction efficiency decreases. In this case, by arranging afilter having a transmittance set depending on each ring area, in thevicinity of the diffractive optical elements D1 and D2, the intensitydistribution of the diffracted light can be made uniform, and as aresult, degradation in the image quality can be prevented.

[0079] The correction surface PL2 formed on the diffractive opticalelements D1 and D2 will now be described. The correction surface PL2 isfor correcting wave front aberration due to any manufacturing error ofthe diffraction pattern surface PL1 of the diffractive optical elementsD1 and D2. A slightly aspheric surface having a sag amount of 0.5 μm orless from a predetermined reference plane, such as a flat surface or aspherical surface is formed thereon. The surface shape of this slightlyaspheric surface can be measured by an interferometer for measuring aspherical surface or a flat surface, for example, Fizeau interferometer.Hence a slightly aspheric surface having a highly precise shape can beformed.

[0080] An other embodiment of the structure of the diffractive opticalelements D1 and D2 will now be described. FIGS. 5A and 5B are diagramsschematically showing an other embodiment of the construction of thediffractive optical elements D1 and D2, with FIG. 5A being a perspectiveview and FIG. 5B being a cross-sectional view. As shown in FIGS. 5A and5B, the diffractive optical elements D1 and D2 have a diffractionpattern surface PL11 formed in rings of concentric circles centered onan optical axis AX, and having a cross-section in a sawtooth shape.Also, there may be formed a correction surface PL12 similar to thecorrection surface PL2 of the diffractive optical elements D1 and D2shown in FIGS. 3A and 3B. As shown in FIGS. 5A and 5B, the diffractionpattern of the sawtooth shape formed in rings in each ring area isformed so that each ring satisfies a certain predetermined diffractionefficiency, with respect to diffracted light of an optional order.

[0081] Moreover, in the case where the cross-section of the diffractiveoptical elements D1 and D2 is made sawtooth shape, if it is assumed thatan area from the optical axis AX to a position a predetermined distanceaway therefrom is a first ring area, and the ring areas outside thereofare a second ring area and a third ring area, and so on, it is desiredthat the first ring area have a sawtooth cross-section so that thediffraction efficiency increases most with the 1st or −1st diffractedlight, and the ring areas outside thereof have a sawtooth cross-sectionso that the diffraction efficiency increases most with the mth or −mthdiffracted light (m is an integer satisfying m>2), taking ease ofproduction into account. By setting in this manner, even if the minimumpitch of each ring is not decreased, the power of the diffractiveoptical elements D1 and D2 can be set high. When diffracted light of ahigher order is used according to the above construction, the angularcharacteristic becomes more disadvantageous. In this embodiment,however, since parallel light is shone onto the diffractive opticalelement D1 by means of the optical system G1 and parallel light is shoneonto the diffractive optical element D2 by means of the optical systemG2, the difference in the angle of incidence of the luminous flux shoneonto the diffractive optical elements D1 and D2 becomes quite small,causing no big problem.

[0082] Moreover, in order to correct the axial chromatic aberration ofthe projection optical system PL, it is necessary to increase the powerof the diffractive optical elements D1 and D2 to a desired order.However, if an attempt is made to manufacture diffractive opticalelements D1 and D2 having a large power, the pitch around thediffractive optical elements D1 and D2 becomes too small. Therefore, ifthe pitch is arranged so that the power decreases gradually from thecentral position of the diffractive optical elements D1 and D2 towardthe periphery thereof, it is possible to prevent the pitch in theperipheral portion becoming too small, while correcting the axialchromatic aberration. However, such a pitch arrangement corrects thespherical aberration too much. Therefore, at least two diffractiveoptical elements, namely diffractive optical element D1 and diffractiveoptical element D2 are arranged in the projection optical system PL, andan aspherical lens is arranged such that at least one sphericalaberration is not corrected excessively, in the optical path between thediffractive optical element D1 and the diffractive optical element D2,or one surface of the optical system G3 is made aspherical, therebyrealizing a projection optical system in which aberration is favorablycorrected. In the case of this embodiment described above, thecorrection surface PL2 or the correction surface PL12 is provided on oneof the diffractive optical elements D1 and D2 for the purpose ofcorrecting any manufacturing error of the diffraction pattern surfacePL1 or the diffraction pattern surface PL11 of the diffractive opticalelements D1 and D2. However, this technical idea is not limited todiffractive optical elements, and can be applied to general opticalelements.

[0083] Next, the situation where the illumination light is irradiatedonto the wafer W via the projection optical system PL described abovewill be described. FIG. 6 is a diagram showing the situation where theillumination light is irradiated onto a wafer via the projection opticalsystem PL. In FIG. 6, of the illumination light emitted from theprojection optical system PL and irradiated onto the wafer W, in view ofthe design, the illumination light irradiated onto the illumination areaEX is the illumination light between the luminous flux denoted by areference symbol r1 and the luminous flux denoted by a reference symbolr2 in the figure. However, since the diffractive optical elements D1 andD2 are used, flare light occurs. The flare light mainly appears in thevicinity of the luminous flux denoted by the reference symbols r11, r12in the figure. Therefore, in order to prevent this flare light frombeing irradiated onto the wafer W, it is desirable to provide a fieldstop 30 between the projection optical system PL and the wafer W.

[0084] Next, an embodiment of the projection optical system PL of thepresent invention will be described.

[0085]FIG. 7 is a cross-sectional view of a lens showing the opticalconstruction of the projection optical system PL according to oneembodiment of the present invention. The wavelength λ in this embodimentis 157.6244 nm. In FIG. 7, the projection optical system PL isconstituted by arranging, in order from a reticle R (object surface)side arranged on the first plane P1, a first lens group G11 having apositive refracting power, a second lens group G12 having a negativerefracting power, a diffractive optical element D11 having a positivepower, a negative meniscus lens L24 having a negative refracting power,with the concave surface facing the first plane P1, a diffractiveoptical element D12 having a positive power, and a third lens group G13having a positive refracting power. This projection optical system istelecentric both on the reticle R (object surface) side, and on thewafer W (image surface) side arranged on the second plane P2. The firstlens group G11 and the second lens group G12 correspond to the opticalsystem G1 in FIG. 2, the diffractive optical element D11 and thediffractive optical element D12 correspond to the diffractive opticalelement D1 and the diffractive optical element D2 in FIG. 2,respectively, the negative meniscus lens L24 corresponds to the opticalsystem G2 in FIG. 2, and the third lens group 13 corresponds to theoptical system G3 in FIG. 1.

[0086] The first lens group G11 comprises eight lenses arranged therein,in order from the first plane P1 side namely; a negative meniscus lensL11 with the concave surface facing the second plane P2, adouble-concave lens L12, a positive meniscus lens L13 with the convexsurface facing the second plane P2 side, a double-convex lens L14, adouble-convex lens L15, a positive meniscus lens L16 with the convexsurface facing the first plane P1 side, a negative meniscus lens L17with the concave surface facing the second plane P2 side, and a negativemeniscus lens L18 with the concave surface facing the second plane P2side. Here, the surface c4 of the negative meniscus lens L11 on thefirst plane P1 side, the surface c2 of the double-concave lens L12 onthe second plane P2 side, and the surface c3 of the negative meniscuslens L17 on the second plane P2 side are formed aspheric.

[0087] The second lens group G12 comprises five lenses arranged therein,in order from the first plane P1 side namely; a double-concave lens L19,a double-concave lens L20, a negative meniscus lens L21 with the concavesurface facing the first plane P1 side, a positive meniscus lens L22with the convex surface facing the second plane P2 side, and a positivemeniscus lens L23 with the convex surface facing the first plane P1side. Here, the surface c4 of the double-concave lens L20 on the secondplane P2 side is formed aspheric. The diffractive optical element D11and the diffractive optical element D12 are designed so as to have adifferent diffraction characteristics depending on the position thereof.Therefore, in this embodiment, the diffractive optical element D11 andthe diffractive optical element D12 are handled as with aspheric surfacelenses, to perform aberration calculation. Between the negative meniscuslens L24 and the diffractive optical element D12, there is arranged avariable aperture stop AS for determining the numerical aperture (NA) ofthe projection optical system PL.

[0088] The third lens group G13 comprises five lenses arranged therein,in order from the first plane P1 side namely; a double-convex lens L25,a positive meniscus lens L26 with the convex surface facing the firstplane P1 side, a positive meniscus lens L27 with the convex surfacefacing the first plane P1 side, a positive meniscus lens L28 with theconvex surface facing the first plane P1 side, and a positive meniscuslens L29 with the convex surface facing the first plane P1 side. Here,the surface c5 of the positive meniscus lens L28 on the second plane P2side is formed aspheric.

[0089] Parameter values of the projection optical system PL according tothe one embodiment of the present invention are shown below. Here, thesurface c1 of the negative meniscus lens L11 on the first plane P1 side,the surface c2 of the double-concave lens L12 on the second plane P2side, the surface c3 of the negative meniscus lens L17 on the secondplane P2 side, the surface c4 of the double-concave lens L20 on thesecond plane P2 side and the surface c5 of the positive meniscus lensL28 on the second plane P2 side, in the projection optical system PL,are formed aspheric, respectively, and these surfaces are expressed bythe following expression (3). $\begin{matrix}{Z = {\frac{\rho \cdot Y^{2}}{\begin{matrix}{1 + \sqrt{\left( {1 - {\left( {1 + \kappa} \right) \cdot \rho^{2} \cdot Y^{2}}} \right)} +} \\{{(E) \cdot Y^{12}} + {(F) \cdot Y^{14}} + {(G) \cdot}} \\{Y^{16} + {(H) \cdot Y^{18}} + {(J) \cdot Y^{20}}}\end{matrix}} + {(A) \cdot Y^{4}} + {(B) \cdot Y^{6}} + {(C) \cdot Y^{8}} + {(D) \cdot Y^{10}}}} & (3)\end{matrix}$

[0090] wherein, in the above expression (3),

[0091] z: deviation from a tangent plane being in contact with the lenson the optical axis (sag amount);

[0092] ρ: curvature;

[0093] Y: distance from the optical axis;

[0094] k: conic projection;

[0095] A: quartic aspherical coefficient;

[0096] B: sixth order aspherical coefficient;

[0097] C: eighth order aspherical coefficient;

[0098] D: tenth order aspherical coefficient;

[0099] E twelfth order aspherical coefficient;

[0100] F: fourteenth order aspherical coefficient;

[0101] G: sixteenth order aspherical coefficient;

[0102] H: eighteenth order aspherical coefficient;

[0103] J twentieth order aspherical coefficient.

[0104] Moreover, the diffractive optical element D11 and the diffractiveoptical element D12 are designed by an ultra-high index methoddesignating a virtual refractive index as 1001.

[0105] Table 1 shown below is a table showing parameter values of theprojection optical system PL according to the one embodiment of thepresent invention. The unit of numerical values shown in Table 1 ismillimeters, and is rounded to three places after the decimal point. Thedistance from the position on the first plane P1 to the surface c1 ofthe negative meniscus lens L11 on the first plane P1 side in FIG. 7 isset to be 55 mm, the distance from the surface of the positive meniscuslens L29 on the second plane P2 side to the second plane P2 is set to be13.196 mm, and the distance from the first plane P1 to the second planeP2 is set to be 986 mm. Meanwhile, the focal length of the diffractiveoptical element D11 is 509.8 mm, and the focal length of the diffractiveoptical element D12 is 702.9 mm. Moreover, the value of 1/|NA·β| shownin the above described expression (1) is 0.122, and the value of f/Lshown in the above described expression (2) is 0.517.

[0106] The glass material of each lens is fluorite, and the refractiveindex of fluorite in the used wavelength is 1.559, and the dispersion(dn/dλ) is −2.605E-6/pm. Also, in Table 1, fluorite is mentioned as thesubstrate of the diffractive optical elements D11 and D12, but thissubstrate is not limited to fluorite, and for example, quartz or quartzhaving no hydroxyl group mixed therein, may be used.

[0107] However, in Table 1, the numerical aperture of the projectionoptical system PL on the second plane P2 side is 0.75, with themagnification being ¼, the field image being φ 23 m, and the field ofview being a rectangular shape of 22×6 mm. Moreover, in Table 1, theleftmost figure is the order of the lens surface from the first plane P1side, r denotes a radius of curvature of the lens surface, and d denotesa space from a lens surface to the next lens surface. Also, in Table 1,in order to facilitate the arrangement of each lens, glass materialsfrom one lens surface to the next lens surface are shown. TABLE 1Surface Number r d Glass Material 1: (asphere) 3898.447 13.306 fluorite2: 486.711 16.403 3: −168.587 23.207 fluorite 4: (asphere) 2227.72610.443 5: −327.045 49.709 fluorite 6: −215.624 1.000 7: 1696.173 28.030fluorite 8: −325.178 1.000 9: 521.134 32.820 fluorite 10: −419.204 1.00011: 171.992 25.652 fluorite 12: 330.412 4.280 13: 139.024 32.100fluorite 14: (asphere) 128.269 10.277 15: 183.435 36.732 fluorite 16:102.175 30.874 17: −260.834 13.139 fluorite 18: 420.621 67.092 19:−97.580 16.089 fluorite 20: (asphere) 463.064 26.354 21: −136.183 39.289fluorite 22: −154.619 1.000 23: −305.514 34.294 fluorite 24 −143.3684.468 25: 229.134 37.386 fluorite 26: 2869.502 3.441 27: ∞ 15.000fluorite (substrate of D11) 28: ∞ 0.000 29: (asphere) −509824.084 25.911(diffractive optical element D11) 30: −312.844 20.257 fluorite 31:−174441.248 20.000 32: ∞ 32.069 (opening AS) 33: ∞ 15.000 fluorite(substrate of D12) 34 ∞ 0.000 35: (asphere) −702884.42 34.402(diffractive optical element D12) 36: 692.885 30.706 fluorite 37:−744.752 2.453 38: 418.127 27.577 fluorite 39: 40398.612 1.538 40:155.116 40.970 fluorite 41: 167.602 4.018 42: 108.981 38.699 fluorite43: (asphere) 789.046 14.481 44 361.204 35.201 fluorite 45: 1755.193

[0108] Moreover, of each lens surface shown in the above Table 1, theaspherical coefficients related to the aspherical surfaces are shown inTable 2. TABLE 2 First Surface κ: 0.000 A: 0.173E−06 B: −.100E−10 C:0.558E−15 D: −.395E−19 E: 0.433E−23 F: −.453E−27 G: 0.000E+00 H:0.000E+00 J: 0.000E+00 Fourth Surface κ: 0.000 A: 0.481E−07 B: −.587E−11C: 0.370E−15 D: −.848E−20 E: −.782E−24 F: 0.550E−28 G: 0.000E+00 H:0.000E:+00 J: 0.000E:+00 Fourteenth Surface κ: 0.000 A: 0.193E−08 B:0.152E−11 C: 0.266E−16 D: 0.727E−20 E: −.325E−24 F: 0.837E−28 G:0.000E:+00 H: 0.000E:+00 J: 0.000E:+00 Twentieth Surface κ: 0.000 A:0.872E−08 B: −.233E−11 C: 0.121E−15 D: −.929E−20 E: 0.471E−24 F:−.111E−28 G: 0.000E:+00 H: 0.000E:+00 J: 0.000E+00 Twenty-ninth Surfaceκ: 0.000 A: 0.123E−10 B: −.491E−16 C: −.334E−20 D: −.876E−25Thirty-fifth Surface κ: 0.000 A: 0.449E−11 B: 0.342E−15 C: −.635E−22 D:0.800E−25 Forty-third Surface κ: 0.000 A: 0.393E−08 B: 0.359E−11 C:−.150E−15 D: −.199E−19 E: 0.554E−23 F: −.422E−27 G: 0.000E:+00 H:0.000E:+00 J: 0.000E:+00

[0109]FIG. 8 is a diagram showing a transverse aberration diagram(comatic aberration diagram) in the tangential direction and the sagitaldirection in the first embodiment of the projection optical system PLaccording to one embodiment of the present invention. In each aberrationdiagram, a solid line shows a case where the wavelength of light is157.6244 (=λ) nm, and a dotted line shows a case where the wavelength oflight is λ+1.1 pm, and a dashed line shows a case where the wavelengthof light is λ−1.1 pm. Here, the unit of numerical values shown in FIG. 8is millimeter, and shown in order from the top, is a case where theheight of the image on the wafer W is 11.5 mm, a case where this is 6mm, and a case where this is 0 mm. From these aberration diagrams, it isseen that in the first embodiment, aberration is very small in thewavelength λ. Moreover, even in the case of a wavelength deviated fromthe wavelength λ, it is seen that a large chromatic aberration does notoccur. In this case, the minimum pitch formed on the diffractive opticalelement D1 is 1.00 μm, and the minimum pitch formed on the diffractiveoptical element D12 is 1.52 μm. According to this embodiment, the imageon the first plane can be formed on the second plane under suitableconditions, using extreme ultraviolet illumination light.

[0110]FIG. 9 is a cross-sectional view of a lens showing the opticalconstruction of the projection optical system PL according to an otherembodiment of the present invention. The wavelength λ in this embodimentis 157.6244 nm, as in the embodiment shown in FIG. 7. In FIG. 9, theprojection optical system PL is constituted by arranging, in order froma reticle R (object surface) side arranged on the first plane P1, afirst lens group G21 having a positive refracting power, a second lensgroup G22 having a negative refracting power, a diffractive opticalelement D21 having a positive power, a double-concave lens L54, adiffractive optical element D22 having a positive power, and a thirdlens group G23 having a positive refracting power. This projectionoptical system is telecentric both on the reticle R (object surface)side, and on the wafer W (image surface) side arranged on the secondplane P2, as in the first embodiment. The first lens group G21 and thesecond lens group G22 correspond to the optical system G1 in FIG. 2, thediffractive optical element D21 and the diffractive optical element D22correspond to the diffractive optical element D1 and the diffractiveoptical element D2 in FIG. 2, respectively, the double-concave lens L54corresponds to the optical system G2 in FIG. 2, and the third lens group13 corresponds to the optical system G3 in FIG. 1.

[0111] The first lens group G21 comprises eight lenses arranged therein,in order from the first plane P1 side namely; a double-concave lens L41,a double-concave lens L12, a negative meniscus lens L42 with the concavesurface facing the first plane P1 side, a positive meniscus lens L43with the convex surface facing the second plane P2 side, a double-convexlens L44, a double-convex lens L45, a positive meniscus lens L46 withthe convex surface facing the first plane P1 side, a positive meniscuslens L47 with the convex surface facing the first plane P1 side, and anegative meniscus lens L48 with the concave surface facing the secondplane P2 side. Here, the surface c1 of the double-concave lens L41, thesurface c12 of the double-concave lens L12 on the second plane P2 side,and the surface c13 of the positive meniscus lens L47 on the secondplane P2 side are formed aspheric.

[0112] The second lens group G22 comprises five lenses arranged therein,in order from the first plane P1 side namely; a double-concave lens L49,a double-concave lens L50, a negative meniscus lens L51 with the concavesurface facing the first plane P1 side, a positive meniscus lens L52with the convex surface facing the second plane P2 side, and adouble-convex lens 53. Here, the surface c14 of the double-concave lensL50 on the second plane P2 side is formed aspheric. The diffractiveoptical element D21 and the diffractive optical element D22 are alsodesigned so as to have a different diffraction characteristic dependingon the position thereof. As in the first embodiment, the diffractiveoptical element D21 and the diffractive optical element D22 are handledas with the aspheric lenses, to perform aberration calculation. Also, inthis embodiment, the surface c15 of the double-concave lens L54 on thesecond plane P2 side, arranged between the diffractive optical elementD21 and the diffractive optical element D22 is designed aspheric.Between the double-concave lens L54 and the diffractive optical elementD22, there is arranged a variable aperture stop AS for determining thenumerical aperture (NA) of the projection optical system PL.

[0113] The third lens group G23 comprises five lenses arranged therein,in order from the first plane P1 side namely; a double-convex lens L55,a positive meniscus lens L56 with the convex surface facing the firstplane P1 side, a positive meniscus lens L57 with the convex surfacefacing the first plane P1 side, a positive meniscus lens L58 with theconvex surface facing the first plane P1 side, and a convex plano-lensL59. Here, the surface c16 of the positive meniscus lens L58 on thesecond plane P2 side is formed aspheric.

[0114] Table 3 shown below is a table showing parameter values of theprojection optical system PL according to the other embodiment of thepresent invention. The unit of numerical values shown in Table 3 ismillimeter, and is rounded to three places after the decimal point. Thedistance from the position on the first plane P1 to the first surfacec11 of the double-concave lens L41 on the first plane P1 side in FIG. 9is set to be 55 mm, the distance from the surface of the convexplano-lens L59 on the second plane P2 side to the second plane P2 is setto be 13.000 mm, and the distance from the first plane P1 to the secondplane P2 is set to be 1024 mm. Meanwhile, the focal length of thediffractive optical element D21 is 484.0 mm, and the focal length of thediffractive optical element D22 is 660.0 mm. Moreover, the value of1/|NA·β| shown in the above described expression (1) is −0.010, and thevalue of f/L shown in the above described expression (2) is 0.473. Theglass material of each lens is fluorite, and the refractive index offluorite in the used wavelength is 1.559, and the dispersion (dn/dλ) is−2.605E-6/pm.

[0115] However, in Table 3, the numerical aperture of the projectionoptical system PL on the second plane P2 side is 0.75, with themagnification being ¼, the field image being φ 23 m, and the field ofview being a rectangular shape of 22×6 mm. Moreover, in Table 3, theleftmost figure is the order of the lens surface from the first plane P1side, r denotes a radius of curvature of the lens surface, and d denotesa space from a lens surface to the next lens surface. Also, in Table 3,in order to facilitate the arrangement of each lens, glass materialsfrom one lens surface to the next lens surface are shown.

[0116] Furthermore, in Table 3, fluorite is mentioned as the substrateof the diffractive optical elements D21 and D22, but this substrate isnot limited to fluorite, and for example, quartz or quartz having nohydroxyl group mixed therein may be used, as with the embodiment shownin FIG. 7. Moreover, the diffractive optical element D21 and thediffractive optical element D22 are designed by an ultra-high indexmethod designating a virtual refractive index as 1001, as with theembodiment shown in FIG. 7. TABLE 3 Surface Number r d Glass Material 1:(asphere) −1369.992 16.233 fluorite 2: 290.313 21.361 3: −171.363 15.555fluorite 4: (asphere) −3754.999 7.864 5: −504.939 49.546 fluorite 6:−203.373 2.176 7: 34133.009 33.313 fluorite 8: −210.834 1.000 9: 618.91425.606 fluorite 10: −660.786 1.000 11: 149.583 29.844 fluorite 12:307.782 1.000 13: 140.106 29.162 fluorite 14: (asphere) 172.830 9.84815: 421.804 23.405 fluorite 16: 103.521 31.676 17: −260.885 18.193fluorite 18: 433.853 80.189 19: −99.106 30.213 fluorite 20: (asphere)674.459 28.426 21: −124.630 38.330 fluorite 22: −143.905 1.000 23:−612.558 32.321 fluorite 24 −200.000 1.000 25: 1174.146 41.004 fluorite26: −292.606 1.000 27: ∞ 15.000 fluorite (substrate of D21) 28: ∞ 0.00029: (asphere) −484309.817 40.728 (diffractive optical element D21) 30:−2397.653 20.257 fluorite 31: (asphere) 360.526 42.700 32: ∞ 48.118(opening AS) 33: ∞ 13.013 fluorite (substrate of D22) 34 ∞ 0.000 35:(asphere) −659916.992 16.667 (diffractive optical element D22) 36:729.160 29.578 fluorite 37: −729.160 3.317 38: 462.425 23.973 fluorite39: 14595.759 1.221 40: 315.432 23.545 fluorite 41: 356.945 1.000 42:131.719 43.074 fluorite 43: (asphere) 1380.673 18.685 44 272.686 45.834fluorite 45: ∞

[0117] Moreover, of each lens surface shown in the above Table 3, theaspherical coefficients related to the aspherical surfaces are shown inTable 4. TABLE 4 First Surface κ: 0.000 A: 0.206E−06 B: −.182E−10 C:0.111E−14 D: −.168E−18 E: 0.322E−22 F: −.349E−26 G: 0.000E+00 H:0.000E:+00 J: 0.000E+00 Fourth Surface κ: 0.000 A: 0.947E−07 B:−.110E−10 C: 0.306E−15 D: 0.246E−19 E: −.298E−23 F: 0.379E−28 G:0.000E+00 H: 0.000E:+00 J: 0.000E+00 Fourteenth Surface κ: 0.000 A:−.561E−07 B: 0.756E−12 C: −.984E−16 D: −.187E−20 E: −.208E−24 F:−.712E−30 G: 0.000E:+00 H: 0.000E:+00 J: 0.000E:+00 Twentieth Surface κ:0.000 A: 0.514E−07 B: −.323E−11 C: 0.376E−16 D: 0.11613−19 B: −.918E−24F: 0.171E−28 G: 0.000E+00 H: 0.000E+00 J: 0.000E+00 Twenty-ninth Surfaceκ: 0.000 A: 0.15013−10 B: 0.71713−16 C: 0.41613−20 D: 0.528E−26Thirty-first Surface κ: 0.000 A: −.210E−07 B: −.117E−12 C: −.55913−17 D:0.637E−21 B: −.19313−26 F: 0.578E−30 G: 0.000E+00 H: 0.000E+00 J:0.000E:+00 Thirty-fifth Surface κ: 0.000 A: 0.516E−11 B: 0.77813−16 C:−.15813−20 D: −.948E−25 Fourth-third Surface κ: 0.000 A: −.166E−08 B:0.36813−11 C: −.349E−15 D: 0.361E−19 E: −.305E−23 F: 0.14113−27 G:0.000E:+00 H: 0.000E:+00 J: 0.000E:+00

[0118]FIG. 10 is a diagram showing a transverse aberration diagram(comatic aberration diagram) in the tangential direction and the sagitaldirection of the projection optical system PL according to the otherembodiment of the present invention. In each aberration diagram, a solidline shows a case where the wavelength of light is 157.6244 (=λ) nm, anda dotted line shows a case where the wavelength of light is λ+1.1 pm,and a dashed line shows a case where the wavelength of light is λ−1.1pm. Here, the unit of numerical values shown in FIG. 10 is millimeters,and shown in order from the top is a case where the height of the imageon the wafer W is 11.5 mm, a case where this is 6 mm, and a case wherethis is 0 mm. From these aberration diagrams, it is seen that also inthis embodiment, aberration is very small in the wavelength λ. Moreover,even in the case of a wavelength deviated from the wavelength λ, it isseen that a large chromatic aberration does not occur In this case, theminimum pitch formed on the diffractive optical element D21 is 1.14 μm,and the minimum pitch formed on the diffractive optical element D22 is1.20 μm. According to the above embodiment, the image on the first planecan be formed on the second plane under suitable conditions, usingextreme ultraviolet illumination light.

[0119] The projection optical system PL in each embodiment of thepresent invention has been described above. Next, an embodiment of amanufacturing method for micro devices will be described, wherein theexposure apparatus and the exposure method according to one embodimentof the present invention are used in the lithography process. FIG. 11 isa flowchart showing a manufacturing example for micro devices(semiconductor chips such as ICs and LSIs, liquid crystal panels, CCDs,thin film magnetic heads, micro-machines, etc.). As shown in FIG. 11, atfirst in step S11 (designing step), designing of function andperformance of micro devices (for example, circuit designing ofsemiconductor devices) is performed, and pattern designing is performedfor realizing the function. Subsequently, in step S11 (mask productionstep), a mask (reticle) having the designed circuit pattern formedthereon is manufactured. On the other hand, in step S12 (waferproduction step), a wafer is manufactured, using a material such assilicon.

[0120] Next, in step S13 (wafer processing step), an actual circuit orthe like is formed on the wafer by a lithography technique or the like,as described below, using the mask and the wafer prepared in the stepsS10 to S12. Then, in step S14 (device assembly step), a device isassembled using the wafer processed in step S13. This step S14 includesa dicing step, a bonding step and a packaging step (chip filling),according to need. Lastly, in step S15 (inspection step), inspectionssuch as a program operation test and a durability test are performed,with respect to micro devices manufactured in step S14. Micro devicesare completed through these steps, and then shipped.

[0121]FIG. 12 is a diagram showing one example of a detailed flow instep S13 in FIG. 11, in the case of manufacturing semiconductor devices.In FIG. 12, in step S21 (oxidization step), the surface of the wafer isoxidized. In step S22 (CVD step), an insulation film is formed on thewafer surface. In step S23 (electrode formation step), an electrode isformed on the wafer by deposition. In step S24 (ion implantation step),ions are implanted in the wafer. Respective steps of step S21 to stepS24 constitute a pre-processing process for each stage of waferprocessing, which are selected according to the necessary processing ineach stage and executed.

[0122] In each stage of the wafer processing, when the above describedpre-processing process is completed, the post-processing process isexecuted in the following manner. In this post-processing process, atfirst in step 25 (resist formation step), a photosensitizer is appliedon the wafer. Subsequently, in step 26 (exposure step), the circuitpattern on the mask is transferred onto the wafer by the above describedlithography system (exposure apparatus) and exposure method. Then, instep 27 (development step), the exposed wafer is developed, and in step28 (etching step), the exposed member in a portion other than theportion where the resist remains is removed by etching. Then, in step 29(resist removal step), the resist which becomes unnecessary afteretching has been finished, is removed. By repeating these pre-processingprocesses and post-processing processes, multiple circuit patterns areformed on the wafer.

[0123] If the micro device manufacturing method in this embodimentdescribed above is used, the above described exposure apparatus andexposure method are used in the exposure step (step 26), enablingimprovement in resolution by means of the exposure light in the vacuumultraviolet region, and further, exposure amount control can beperformed with high precision. As a result, highly integrated devices inwhich the minimum line breadth is about 0.1 μm can be manufactured athigh yield.

[0124] Furthermore, the present invention is applicable to exposureapparatus in which a circuit pattern is transferred from a motherreticle to a glass substrate, a silicon wafer or the like, in order tomanufacture not only micro devices such as semiconductor devices, butalso a reticle or mask used in optical exposure apparatus, EUV exposureapparatus, X-ray exposure apparatus, electron beam exposure apparatus orthe like. Here, in the exposure apparatus using DUV (deep ultraviolet)or VUV (vacuum ultraviolet) light, a transmission type reticle isgenerally used, and quartz glass, quartz glass in which fluorine isdoped, fluorite, magnesium fluoride or quartz crystal is used for thereticle substrate. In the proximity type X-ray exposure apparatus orelectron beam exposure apparatus, transmission type masks (stencil mask,membrane mask) are used, and a silicon wafer or the like is used for themask substrate. Such exposure apparatus are disclosed in WO 99/34255, WO99/50712, WO 99/66370, and Japanese Unexamined Patent Applications,First Publication Nos. Hei 11-194479, 2000-12453, 2000-29202.

[0125] Needless to say, the present invention is applicable not only toexposure apparatus used for production of semiconductor devices, butalso to exposure apparatus used for production of displays includingliquid crystal devices (LCDs) to transfer a device pattern onto a glassplate, exposure apparatus used for production of thin film magneticheads to transfer a device pattern onto a ceramic wafer, and exposureapparatus used for production of imaging elements such as CCDs.

What is claimed is:
 1. A projection optical system which forms an imageon a first plane on a second plane, comprising: a first diffractiveoptical element arranged in an optical path between said first plane andsaid second plane; a second diffractive optical element arranged in theoptical path on the side of said second plane from said firstdiffractive optical element; and an optical system having a negativepower, arranged in the optical path between said first diffractiveoptical element and said second diffractive optical element.
 2. Aprojection optical system according to claim 1, further comprising: afront optical system arranged between said first plane and said firstdiffractive optical element; and a rear optical system arranged betweensaid second diffractive optical element and said second plane; and saidfront optical system converts an axial luminous flux on said first planeto a substantially parallel luminous flux, and guides said parallelluminous flux to said first diffractive optical element; and saidoptical system having a negative power converts an axial luminous fluxon said first plane via said first diffractive optical element again toa substantially parallel luminous flux, and guides said parallelluminous flux to said second diffractive optical element.
 3. Aprojection optical system which forms an image on a first plane on asecond plane, comprising: a diffractive optical element arranged in anoptical path between said first plane and said second plane; and anoptical system arranged in the optical path between said first plane andsaid diffractive optical element; wherein when a numerical aperture onthe side of said second plane of said projection optical system isdesignated as NA, an imaging magnification of said optical systems fromsaid first plane to immediately before said diffractive optical elementis designated as β, the focal length of said diffractive optical elementwith respect to a predetermined wavelength is designated as f, and thedistance from said first plane to said second plane is designated as L,said projection optical system satisfies the following conditions:1/|NA·β|0.7 0.38<f/L<1.2.
 4. A projection optical system having aplurality of optical elements arranged along an optical path between afirst plane and a second plane for forming an image on the first planeon the second plane, wherein at least one diffractive optical elementhaving a diffraction pattern surface formed on one surface and acorrection surface formed on an other surface is arranged along saidoptical path, and said correction surface corrects a manufacturing erroron said diffraction pattern surface.
 5. A projection optical systemaccording to claim 4, wherein said correction surface has a slightlyaspheric surface which has been subjected to aspheric surface processingwith a sag amount of 0.5 μm or less with respect to a predeterminedreference plane.
 6. A projection optical system according to claim 5,wherein said reference plane is a flat or spherical surface.
 7. Aprojection optical system according to claim 1, wherein all thediffraction patterns of said diffractive optical elements are formed ona flat substrate.
 8. A projection optical system according to claim 1,wherein diffraction patterns of said diffractive optical elements areformed in a plurality of ring areas centered on an optical axis, saideach ring area being formed of a binary optical element approximated ina plurality of stages by a plurality of surfaces, and said binaryoptical element formed in said each ring area has a positive power,respectively.
 9. A projection optical system according to claim 8,wherein at least one stage number of the binary optical elementsrespectively formed in said each ring area is different from the stagenumber of other binary optical elements.
 10. A projection optical systemaccording to claim 8, wherein a filter having a different transmittanceaccording to each ring area is arranged in the vicinity of saiddiffractive optical element.
 11. A projection optical system accordingto claim 1, wherein the diffraction patterns of said diffractive opticalelements are formed in a plurality of ring areas centered on an opticalaxis, each of said respective ring areas having a sawtooth cross-sectionhaving a positive power.
 12. A projection optical system according toclaim 11, wherein the diffraction pattern of said diffractive opticalelement is formed in a first ring area and a second ring area, centeredon a mutual optical axis, said first ring area being formed on the sideof the optical axis from said second ring area, and having a sawtoothcross-section in which the diffraction efficiency becomes highest withregard to the 1st or −1st diffracted light, and said second ring areabeing formed on the side of the periphery from said first ring area, andhaving a sawtooth cross-section in which the diffraction efficiencybecomes highest with regard to the mth or −mth diffracted light (m is aninteger equal to or greater than 2).
 13. A projection optical systemaccording to claim 1, wherein said plurality of optical elementsconstituting said projection optical system have lenses contributing toforming an image on the first plane on the second plane, and all thelenses constituting said projection optical system are constituted offluorite.
 14. A projection optical system according to claim 1, whereinsaid optical system having a negative power has an aspheric surface. 15.A projection optical system wherein a plurality of optical elements arerespectively arranged along an optical path between a first plane and asecond plane for forming an image on the first plane on the secondplane, and at least one of said plurality of optical elements has anoptical surface formed on one surface and a correction surface formed onan other surface, and said correction surface corrects a manufacturingerror on said optical surface.
 16. A projection optical system accordingto claim 15, wherein said correction surface has a slightly asphericsurface which has been subjected to an aspheric surface processing witha sag amount of 0.5 μm or less with respect to a predetermined referenceplane.
 17. A projection optical system according to claim 3, wherein anoptical system having a positive power is arranged in the optical pathbetween said diffractive optical element and said second plane, and saidoptical system arranged in the optical path between said first plane andsaid diffractive optical element has a positive power.
 18. An exposureapparatus comprising: a mask stage for setting a mask having apredetermined pattern formed thereon on a first plane; a substrate stagewhich sets a photosensitive substrate on a second plane; an illuminationoptical system which illuminates said mask set on said first plane; anda projection optical system according to claim 1 which performsprojection exposure of a pattern image of said mask on saidphotosensitive substrate.
 19. A manufacturing method of micro devicesincluding: a first setting step for setting a mask having apredetermined pattern on a first plane; a second setting step forsetting a photosensitive substrate on a second plane; an illuminationstep for illuminating said mask; an exposure step for performingprojection exposure of a pattern image of said mask onto saidphotosensitive substrate, using a projection optical system according toclaim 1; and a development step for developing said photosensitivesubstrate to which said image has been transferred.
 20. An exposureapparatus comprising: a mask stage which sets a mask having apredetermined pattern formed thereon on a first plane; a substrate stagewhich sets a photosensitive substrate on a second plane; an illuminationoptical system which illuminates said mask set on said first plane; anda projection optical system according to claim 3, which performsprojection exposure of a pattern image of said mask on saidphotosensitive substrate.
 21. A manufacturing method of micro devicesincluding: a first setting step for setting a mask having apredetermined pattern on a first plane; a second setting step forsetting a photosensitive substrate on a second plane; an illuminationstep for illuminating said mask; an exposure step for performingprojection exposure of a pattern image of said mask onto saidphotosensitive substrate, using a projection optical system according toclaim 3; and a development step for developing said photosensitivesubstrate to which said image has been transferred.
 22. An exposureapparatus comprising: a mask stage which sets a mask having apredetermined pattern formed thereon on a first plane; a substrate stagewhich sets a photosensitive substrate on a second plane; an illuminationoptical system which illuminates said mask set on said first plane; anda projection optical system according to claim 4, which performsprojection exposure of a pattern image of said mask on saidphotosensitive substrate.
 23. A manufacturing method of micro devicesincluding: a first setting step for setting a mask having apredetermined pattern on a first plane; a second setting step forsetting a photosensitive substrate on a second plane; an illuminationstep for illuminating said mask; an exposure step for performingprojection exposure of a pattern image of said mask onto saidphotosensitive substrate, using a projection optical system according toclaim 4; and a development step for developing said photosensitivesubstrate to which said image has been transferred.
 24. An exposureapparatus comprising: a mask stage which sets a mask having apredetermined pattern formed thereon on a first plane; a substrate stagewhich sets a photosensitive substrate on a second plane; an illuminationoptical system which illuminates said mask set on said first plane; anda projection optical system according to claim 15, which performsprojection exposure of a pattern image of said mask on saidphotosensitive substrate.
 25. A manufacturing method of micro devicesincluding: a first setting step for setting a mask having apredetermined pattern on a first plane; a second setting step forsetting a photosensitive substrate on a second plane; an illuminationstep for illuminating said mask; an exposure step for performingprojection exposure of a pattern image of said mask onto saidphotosensitive substrate, using a projection optical system according toclaim 15; and a development step for developing said photosensitivesubstrate to which said image has been transferred.
 26. An opticalelement having an optical surface formed on one surface and a correctionsurface formed on an other surface, and said correction surface correctsa manufacturing error on said optical surface.
 27. An optical elementaccording to claim 26, wherein said optical surface comprises adiffraction pattern surface.
 28. An optical element according to claim26, wherein said correction surface has an aspheric surface which hasbeen subjected to an aspheric surface processing with a sag amount of0.5 μm or less with respect to a predetermined reference plane.
 29. Anoptical element according to claim 27, wherein said correction surfacehas an aspheric surface which has been subjected to an aspheric surfaceprocessing with a sag amount of 0.5 μm or less with respect to apredetermined reference plane.